1. Field of the Disclosure
The present disclosure relates to a video display device using a laser beam, and particularly, relates to a video display device which has improved radiation stability of the laser beam and is visually confirmed with a stable display image.
2. Description of the Related Art
In recent years, a laser beam is applied to a wide range of fields such as an optical recording device, a measuring instrument, a printer, a medical instrument, a business machine, or the like which uses characteristics such as a small size, high efficiency, or high directivity. Particularly, recently, a video display device, which radiates the laser beam from the laser beam source to a projection surface such as a screen or a wall using the laser light source and displays an image, is generally known. When the laser beam source is applied to the video display device, it is necessary to stably display a display image which is visually confirmed by an observer, and thus, a stable radiation of the laser beam source is important. Particularly, in the laser beam source, self heat generation is increased according to the radiation of the laser beam, and in most cases, a change in the temperature of the laser beam source due to the heat generation generates instability of the radiation.
Japanese Unexamined Patent Application Publication No. 2011-117849 suggests a device including a configuration which suppresses the change of the temperature due to the heat generation, in, a light source module 910 shown in FIGS. 12A and 12B. In related art, FIGS. 12A and 12B are views illustrating an object detection device which detects an object inside a target region based on a state of a reflected light when light is projected to a target region, FIG. 12A is a view showing configurations of a light source module 910 and a light receiving module 920 which are configurations of an optical unit in an information acquisition device of an object detection device, and FIG. 12B is a cross-sectional configuration view showing the details of the light source module 910.
The light source module 910 and the light receiving module 920 shown in FIG. 12A are disposed on a long chassis 830 laterally in an X axis direction. The chassis 830 is a plate shape member, which is configured of a metal having high thermal conductivity, and has a function, which radiates heat of components (here, light source module 910 and light receiving module 920) disposed on the chassis 830. Moreover, the light source module 910 shown in FIG. 12B is configured to include a laser beam source 911 including a semiconductor laser, a laser holder 916 holding a laser beam source 911, a temperature conditioning element 912 disposed to be adjacent to the laser holder 916, a temperature sensor 913 disposed to contact a side surface of the laser holder 916, a projection lens 914 projecting the laser beam outside the cover 915 over the entire target region, and a wiring 917 connected to a terminal 911t of the laser beam source 911 and a circuit substrate 801. The temperature conditioning element 912 uses a thermoelectric element such as a Peltier element, adjusts the temperature of the laser beam source 911 by heating or cooling the laser beam source 911 from information of the temperature sensor 913, and causes a wavelength of the laser beam emitted from the laser beam source 911 to be maintained at an optimal wavelength.
However, in the related art, since the temperature sensor 913 is disposed to contact the side surface of the laser holder 916, the temperature sensor indirectly detects the temperature of the laser beam source 911 (CAN) via the laser holder 916. Accordingly, in the configuration, an error occurs between an actual temperature of the laser beam source 911 and the detected temperature of the temperature sensor 913. FIG. 13 is a graph showing a relationship between the detected temperature of the temperature sensor 913 and a wavelength of the laser beam according to the laser beam source 911 in the related art. As shown in FIG. 13, in the laser beam source 911 of the related art, an error occurs between the detected temperature of the temperature sensor 913 and the actual temperature of the laser beam source 911, and thus, due to the error, an error occurs in the wavelength of the laser beam emitted from the laser beam source 911. In general, when the laser beam is applied to the video display device, due to the error of the wavelength, instability occurs on a display image visually confirmed by an observer, and thus, in order to suppress the error of the wavelength of the laser beam, correct temperature management is needed.
Moreover, in the laser holder 916 of the related art, it is described that the thermal conductivity is performed by only the member having the thermal conductivity, and thus, if the thermal conductivity is not favorable, a time lag occurs between the actual temperature of the laser beam source 911 and the detected temperature of the temperature sensor 913. In general, when the laser beam is applied to the video display device, due to time lag, instability occurs on a display image visually confirmed by an observer, and thus, in order to suppress the time lag of the wavelength of the laser beam, a method having improved responsiveness needs.
On the other hand, if the temperature sensor 913 is disposed in the vicinity of the laser beam source 911, the temperature error or the time lag is decreased. However, in this case, there is a problem in that it is not easy to electrically connect the temperature sensor 913 and the circuit substrate 801 to each other. Actually, in the related art, the connection between the temperature sensor 913 disposed to contact the side surface of the laser holder 916 and the circuit substrate 801 is not disclosed, and thus, it is described that the connection method is not easily performed.